1. Field of the Invention
The present invention relates generally to methods for forming thermally flowable layers upon substrates. More particularly, the present invention relates to a method for minimizing substrate to substrate clamp sticking during thermal processing of a thermally flowable layer formed upon a substrate clamped within the substrate clamp.
2. Description of the Related Art
Integrated circuits are formed from semiconductor substrates within and upon whose surfaces are formed resistors, transistors, diodes and other electrical circuit elements. The electrical circuit elements are connected internally and externally to the semiconductor substrate upon which they are formed through patterned conductor layers which are separated by dielectric layers.
Patterned conductor layers for use within integrated circuits are typically formed through patterning through etching methods as are conventional in the art of blanket conductor layers formed upon semiconductor substrates. Most commonly, blanket conductor layers are formed upon semiconductor substrates from low melting temperature metal containing conductor layers formed of low melting temperature conductor metals such as but not limited to aluminum, aluminum alloys, aluminum-silicon alloys, aluminum-copper alloys and aluminum-silicon-copper alloys. Blanket low melting temperature metal containing conductor layers, such as blanket aluminum containing conductor layers, may be formed upon semiconductor substrates through several methods as are conventional in the art, including but not limited to thermally assisted evaporation methods, electron beam assisted evaporation methods and physical vapor deposition (PVD) sputtering methods.
In many of the several methods for forming a blanket low melting temperature metal containing conductor layer, such as a blanket aluminum containing conductor layer, upon a substrate, such as a semiconductor substrate, it is common in the art to employ a substrate clamp which among other functions serves as a fixture for properly positioning the substrate within a blanket low melting temperature metal containing conductor layer deposition tool, such as a blanket aluminum containing conductor layer deposition tool, when forming the blanket low melting temperature metal containing conductor layer, such as the blanket aluminum containing conductor layer, upon the substrate. A schematic plan-view diagram of a substrate clamped within a typical substrate clamp is shown in FIG. 1. Shown in FIG. 1 is a substrate 10 positioned beneath a top member 12 of a substrate clamp. Although FIG. 1 illustrates the top member 12 of the substrate clamp as a circular ring, a substrate clamp having a top member formed with an alternate geometric configuration to accommodate a substrate similarly formed with an alternate geometric configuration is not precluded for use within blanket low melting temperature metal containing conductor layer deposition tooling.
In accord with the cross-section 2--2 as illustrated in FIG. 1, FIG. 2 shows a schematic cross-sectional diagram of a portion of the substrate 10 clamped within the substrate clamp as illustrated in FIG. 1. As shown in FIG. 2, the substrate 10a is positioned within the substrate clamp between the top member 12a of the substrate clamp and a backing member 14a of the substrate clamp. The top member 12a and the backing member 14a are connected through a mechanical means (not shown) otherwise conventional in the art of substrate clamp design and fabrication. Although FIG. 2 illustrates the backing member 14a as a backing plate, a substrate clamp having a backing member formed with an alternate geometric configuration is also not precluded for use within blanket low melting temperature metal containing conductor layer deposition tooling.
While the use of substrate clamps as a means for fixturing substrates within blanket low melting temperature metal containing conductor layer deposition tooling, such as blanket aluminum containing conductor layer deposition tooling, has become quite common in the art of blanket low melting temperature metal containing conductor layer deposition, the use of substrate clamps for fixturing substrates within blanket low melting temperature metal containing conductor layer deposition tooling is not entirely without problems. In particular, it is known in the art that when substrate clamps, such as the substrate clamp whose schematic cross-sectional diagram is illustrated in FIG. 2, are employed as fixtures within blanket low melting temperature metal containing conductor layer deposition tooling and methods, such as blanket aluminum containing conductor layer deposition tooling and methods, there is observed a sticking of a substrate to the top member of the substrate clamp when a blanket low melting temperature metal containing conductor layer, such as a blanket aluminum containing conductor layer, formed upon the substrate clamped within the substrate clamp is thermally processed at elevated temperature (typically in excess of about 350 degrees centigrade for aluminum containing conductor layers, at which temperature aluminum containing conductor alloys typically flow) to form a thermally processed blanket low melting temperature metal containing conductor layer, such as a thermally processed blanket aluminum containing conductor layer. Such sticking of the substrate to the top member of the substrate clamp is undesirable since it is often difficult to remove such a substrate when stuck to the top member of the substrate clamp without damaging either the blanket thermally processed low melting temperature metal containing conductor layer or the substrate. The physical mechanism through which such sticking occurs is illustrated by reference to the schematic cross-sectional diagrams of FIG. 3 and FIG. 4.
Shown n FIG. 3 is a schematic cross-sectional diagram otherwise equivalent to the schematic cross-sectional diagram of the substrate 10a clamped between the top member 12a and the backing member 14a of the substrate clamp as illustrated in FIG. 2, but where there is formed upon the substrate 10a blanket low melting temperature metal containing conductor layer 16a and where there is also formed upon the top member 12a of the substrate clamp a low melting temperature metal containing conductor layer residue 16b. The blanket low melting temperature metal containing conductor layer 16a and the low melting temperature metal containing conductor layer residue 16b are typically formed simultaneously within most blanket low melting temperature metal containing conductor layer deposition tools and methods since most blanket low melting temperature metal containing conductor layer deposition tools and methods, such as blanket aluminum containing conductor layer deposition tools and methods, provide line-of-sight deposition characteristics. For the same reason, the blanket low melting temperature metal containing conductor layer 16a is not formed upon the portion of the substrate 10a shaded by the top member 12a of the substrate clamp.
Shown in FIG. 4 is the results of further processing of the blanket low melting temperature metal containing conductor layer 16a formed upon the substrate 10a as illustrated in FIG. 3. Shown in FIG. 4 is the results of thermal processing of the blanket low melting temperature metal containing conductor layer 16a formed upon the substrate 10a as illustrated in FIG. 3. As is seen within FIG. 4, the low melting temperature metal containing conductor layer residue 16b, when thermally processed simultaneously with the blanket low melting temperature metal containing conductor layer 16a, flows to form the thermally processed low melting temperature metal containing conductor layer residue 16b' which bridges to the thermally processed blanket low melting temperature metal containing conductor layer 16a' by virtue of flow of the thermally processed low melting temperature metal containing conductor layer residue 16b', as indicated by the arrow 17 in FIG. 4.
It is thus towards the goal of eliminating substrate to top member of substrate clamp sticking through a physical mechanism involving flow of a thermally processed low melting temperature metal containing conductor layer residue, such as the thermally processed low melting temperature metal containing conductor layer residue 16b' as illustrated in FIG. 4, that the present invention is specifically directed.
Various aspects of blanket integrated circuit layer deposition tooling and methods, such as blanket low melting temperature metal containing conductor layer deposition tooling and methods, and in particular blanket aluminum containing conductor layer deposition tooling and methods, have been disclosed in the art. For example, Wolf et al., in Silicon Processing for the VLSI Era, Vol. 1--Process Technology, Lattice Press (Sunset Beach, Calif.: 1986), pp. 359-63 disclose several detail of the design and construction of sputter systems employed in depositing various metal layers within integrated circuits. In addition, Parsons et al., in U.S. Pat. No. 4,486,289 disclose for depositing integrated circuit layers within integrated circuits a compact planar magnetron sputtering apparatus with improved magnetic coupling to the cathode of the planar magnetron sputtering apparatus. Further, Dimock et al., in U.S. Pat. No. 4,522,697 and Dimock, in U.S. Pat. No. 0.4,523,985 disclose a method and apparatus for indexing substrate wafers to be transferred from a conventional substrate wafer carrier to a substrate wafer processing apparatus wherein integrated circuit layers may be formed upon the substrate wafers. Yet further, Davis et al., in U.S. Pat. No. 4,836,905 discloses a substrate wafer processing method and apparatus where a substrate wafer when in a face down position within a reactor chamber is exposed to first processing step, preferably a plasma cleaning process step, while the substrate wafer when subsequently moved to a vertical position within the reactor chamber is then exposed to a second processing step, preferably a sputter deposition process step. Through the method and apparatus there is avoided particulate contamination accumulation upon the substrate wafer.
Finally: (1) Ono et al., in "Development of a Planarized Al-Si Contact Filling Technology," 1990 VMIC Conference Proceedings (Jun. 12-13, 1990), pp. 76-82; (2) Chen et al., in "Planarized Aluminum Metallization for Sub-0.5 .mu.m CMOS Technology," IEEE IEDM 90, pp. 90-51 to 90-53; and (3) Park et al., in "Al-PLAPH (ALuminum PLAnarization by Post Heating) Process for Planarized Double Metal CMOS Applications," 1991 VMIC Conference Proceedings (Jun. 11-12, 1991), pp. 326-28, disclose various methods for forming within integrated circuits blanket aluminum containing conductor layers exhibiting sub-micron contacts to substrates or sub-micron via filling properties.
Desirable in the art are methods, materials and/or designs through which substrate clamps employed as fixtures when forming and thermally processing blanket low melting temperature metal containing conductor layers upon substrates clamped within those substrate clamps may be fabricated and/or employed in a fashion such that the substrates do not stick to the substrate clamps. Particularly desirable are methods, materials and/or designs through which substrate clamps employed as fixtures when forming and thermally processing blanket aluminum containing conductor layers upon semiconductor substrates clamped within those substrate clamps may be fabricated and/or employed in a fashion such that the semiconductor substrates do not stick to substrate clamps. It is towards the foregoing goals that the present invention is generally directed.